<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Document</title>
    <style>
        div.content1[title]{
            font-weight: bold;
        }
        input[name=user]{
            background-color: aqua;
        }
        /*div[class]{
            background-color: pink;
        }
        /*div[class^=co]{
            background-color: blue;
        }*/
    </style>
</head>
<body>
    <div class="content1" title="内容">content1</div>
    <div class="content2">content1</div>

    <form action="">
        <input type="text" name="account">
        <input type="text" name="user">
    </form>
</body>
</html>